The title cobalt(III) complexes have been investigated by polarized absorption and Raman spectroscopies of the single crystals. The symmetry properties of the d-electron orbitals and of the vibrational modes attributable to the Raman bands of trans(Cl-2)[CoCl2(NH3)(n)(H2O)(4-n)]Cl complexes (n = 2,3, or 4) were examined to elucidated the peculiar observation that ligand substitution causes no splitting of the 15200-cm(-1) absorption band and the 250-cm(-1) Raman band. Effects of replacing the NH3 ligand with H2O on the electronic structure, atom-atom force constants and vibrational modes of these complex ions are briefly described. (c) 2007 Elsevier B.V. All rights reserved.